PHYLUM ARTHROPODA 



365 



The saw-flies (Tenthredinid^e, Fig. 305) are not generally- 

 noticed as adults, but their larvae, which feed on the leaves of 



Fig. 305. — Order Hymenoptera. Saw-fly, Nematus ventricosus. a, adult 

 female ; b, larvae (currant worms) ; c, adult male. (From Report State Ento- 

 mologist of Minnesota.) 



the rose, currant, pear, willow, and larch, are only too well known. 

 The eggs are usually laid in slits made in plant tissue by the 

 saw-like ovipositor of the female. The larvae possess usually 

 from six to eight pairs of abdominal legs and can thus be dis- 

 tinguished from the larvae 

 of Lepidoptera, which 

 have not more than five 

 pairs. Some adult saw- 

 flies lay eggs which develop 

 parthenogenetically. 



The c hale id-flies (Chal- 

 cidid^e, Fig. 306) are 

 minute parasites which 

 perform a service of in- 

 estimable value to man, 



since they attack the eggs, caterpillars, and adults of many 

 injurious insects. The eggs are laid on or in the host and 

 the larvae slowly devour its soft parts. One species, Blasto- 



Fig. 306.- — Order Hymenoptera. Chal- 

 cid-fly, Prospalta murtfeldtii. (From Insect 

 Life.) 



